DE102007024677A1 - A method for producing a container of thermoplastic by extrusion blow molding and connecting element for use in such a method - Google Patents

Abstract

The invention relates to a method for producing a container made of thermoplastic material by extrusion blow molding, wherein the container is provided during its formation within a multi-part tool with at least one of its wall passing through connection element (3). The connecting element (3) according to the invention is formed in two parts, wherein a part is designed as a removable cutting element (11). The cutting element (11) serves as a penetration tip for piercing the wall of the container in the still plastic state (Figure 1).

Description

The The invention relates to a method for producing a container made of thermoplastic material by extrusion blow molding as well a connector for use in such a method.

The The invention relates in particular to a process for the preparation of a Fuel tank made of thermoplastic material as well a connection element for such a fuel tank.

Fuel tank made of thermoplastic material are basically intended for Hydrocarbons are impermeable. These are usually off produced multilayer coextrudates, the barrier layers for hydrocarbons. The for the Production of plastic fuel tanks used Plastics, such as polyethylene, are basically non-diffusion-tight for hydrocarbons. These plastics In addition, they tend to swell in the presence of fuel. Out For this reason, the known fuel tank are made Plastic provided with a multi-layered wall into which a EVOH layer embedded as a barrier to hydrocarbons is. In that regard, the lack of diffusion resistance of the used Base material is no problem.

Usually However, fuel tanks are provided with internals, these have ventilation and ventilation lines and electrical Connections on. For making feedthroughs through the tank wall it is known the finished container To provide with Auskreisungen, in the connection means, valves or the like, are used. The valves, valve covers and Nipples are connected to the outer wall of the container covering the respective opening welded. Such Place connection points on a fuel tank potential leaks. Leakage is not the loss of fluid to understand in the true sense, but are hereby diffusion leaks or Diffusion losses in the area of seams and / or welds meant without additional barrier measures. Around Leakage paths at connections of the fuel tank To avoid it is known, connecting means and valves as elaborate Produce two-component components, which is usually this Components at least a part of a weldable with the tank wall plastic have functional parts on such elements, however, regularly Made of plastics that are not in the presence of fuel sources. These plastics are usually not with the for the Tank wall used plastics welded.

A method for producing a fuel tank made of thermoplastic material and such a fuel tank with connection elements for hoses or the like, for example, from EP 1 211 196 known. The EP 1 211 196 A1 describes a two-shell thermoplastic fuel tank with a barrier layer for hydrocarbons embedded in the tank wall, the shells of which have been joined to the tank obtained by thermoforming. In order to ensure a simple attachment of connecting elements while maintaining a high permeation density for hydrocarbons, is in the EP 1 211 196 A1 proposed a two-piece connection element or a two-part fitting, which comprises at least one outer part and an inner part, wherein the outer part is welded to the container outer wall and the inner part at least partially passes through the outer part under displacement and interposition of the container wall. This arrangement has the advantage that the container wall is enclosed and displaced between the components in such a way that the displaced material serves as a seal for the passage.

A such passage through the container wall is relatively proportionate when thermoforming the half-shells of the container easy to produce, but more difficult is such a connection in the manufacture of a fuel tank by extrusion blow molding to realize.

Of the The invention is therefore based on the object, a process for the preparation a container, in particular a fuel tank to provide thermoplastic material, with which it is possible, connecting elements during manufacture the container with the simplest possible means to provide at this. It should be possible leakage paths for hydrocarbons in the wall of the container be avoided or kept to a minimum.

According to the invention a method for producing a container made of thermoplastic material by extrusion blow molding, in which the container during its formation within a multipart Tool with at least one wall passing through its connection element is provided, wherein the wall of the container in still plasticized state is pierced with a part of the connecting element, such that the connection element at least in partial areas with the container wall a substance-liquid connection enters, wherein the connection element with a penetrating tip is provided and the connecting element in the penetration of the Container wall in a tool provided in the die is inserted, which turned away on the connecting element Side of the container wall is arranged or arranged is.

The Penetration tip and the die can be formed so be that the wall of the container in the relevant Area of penetration is opened so that essentially no or only a very slight Ausulpung the container wall is produced. If the diameter of the die is insignificant greater than that of the penetrating tip is the connecting element, is the enforced by the connecting element opening essentially punched out in the wall of the container become. When the connecting element at its through the wall of the Container to be passed end a certain Design for receiving connection components such as pipes or hoses is ensured in this way that the penetration end of the connecting element free from the wall of the container protrudes. It goes without saying for the expert if necessary, during or after removal the container from the tool slightly post-processing may be required.

at the method according to the invention is the connecting element used as a lost mold stamp, the wall of the container pierced from one side. The connection element itself is used as a means of piercing the container wall used and remains as a lost mold punches in the container wall. The tool serves as a die or recording or as an abutment for the through the wall of the fuel tank to be pressed part of the connection element. "Piercing the container wall "within the meaning of the invention should be so Understand that the material in the peripheral region of the opening thus prepared in the wall of the container as small as possible Forming in the sense of a Austulpung learn.

The Method according to the invention expediently comprises the extrusion of two sheet-like preforms, of which each track forms a container tray. The tracks will be in a three-part mold consisting of outer forms and a center shape formed, with the center shape movable or has displaceable component holder, by means of which during molding the container wall components placed on the inner wall can be. According to the invention, it is provided that the connection element in this way from the inside to pushed through the outside through the container wall becomes.

Preferably the connection element is at the penetration of the container wall inserted into a tool provided in the die, which on the the connection element facing away from the container wall is arranged. Such a template can in a simple manner be formed by a recess in the tool. alternative to Such a recess in the tool can insert into the tool have been introduced that after completion of the container the container wall remains.

Conveniently, is used as a connecting element, a nipple, with a circumferential Flange for welding to the container wall is provided. A weld with the container wall takes place on the side of the container facing the circumferential flange instead. In addition, one finds Welding with that part of the circumference of the connecting element instead, which penetrates the container wall.

alternative can the connection element and an example inside the container to be provided functional component integrally connected to each other be so that, for example, the connection element is a part of the penetration the container wall with an integrally formed flange Collar, on the other hand in one piece, for example a valve body, a bubbler or picks up any other plastic component.

Also does not necessarily have the free end of the connection element be designed as a nipple, but this can also be used as a connector, plug-in coupling or the like may be formed.

When Penetration tip, for example, a sleeve-shaped Cutting element application found that by means of a snap or snap connection removable on a complementary locking profile of the connection element is put on. The attached to the connection element removable penetration tip protects the connecting element from it, from the displaced one Plastic clogged or glued. Especially if the connection element from inside to outside the container wall pierces, the penetrating tip after Completion of the container can be easily removed.

It can be provided, for example, that the cutting element several times is used.

The The object underlying the invention is further solved by a connection element for use in a method according to Invention, which is characterized in that it as a tubular Penetration element with a circumferential collar for welding is formed with the container wall, wherein a part of the connecting element provided with a circumferential cutting edge is. Preferably, the connection element is formed in two parts, wherein a part of the connecting element is formed as a removable cutting element is.

One Such cutting element may be sleeve-shaped, for example be formed, this expediently the intended for piercing the wall insertion side encloses the connection element.

If the connection element, for example, as a conventional nipple with to inflate hoses or pipes formed ends, which usually a so-called fir tree profile, it is particularly advantageous when the cutting element concerned profiled pin of the Connection element or the nipple so encloses, that the connection profile of the same does not melt or with thermoplastic Material is glued.

Conveniently, the cutting element is locked to the connection element.

at a variant of the connecting element is this as a nipple with at least formed an outer holding profile, wherein the Holding profile cooperates positively with the cutting element. The Holding profile can this example, a circumferential detent recess have, with one or more latching hooks or latching projections of the Cutting elements cooperates.

The Cutting element is suitably as about cylindrical sleeve with a leading in installation position, formed around circumferential cutting edge. The cutting edge is expediently Wavy, so that the cutting element its leading end is designed as a cutting crown.

at an advantageous variant of the invention Connection element has the cutting element in the longitudinal direction at least one inner subdivision, through which at least one in the cutting direction front and a rear in the cutting direction melt chamber be formed. The displaced when piercing the wall, plasticized thermoplastic material is initially in the front Melting chamber caught. Possibly. The material is also the cutting direction displaced rear melt chamber. This is expediently provided that the melt chambers via at least one Melt channel communicate with each other.

advantageous Embodiments of the invention are described below with reference to a in explained the drawing illustrated embodiment.

It demonstrate:

1 FIG. 2: a schematic view of a first variant of a connection element plugged onto a component holder before it is pushed through the container wall, FIG.

2 FIG. 3 illustrates the piercing of the container wall by means of the connection element according to the invention and FIG

3 shows schematically the remaining in the container wall connection element and the process of removing the cutting element and

4 A second variant of a connection element according to the invention.

In 1 is only part of a wall of a blow mold 1 shown schematically. The complete glass tool as well as the associated extruders and removal devices and the like are not shown for reasons of simplicity.

The Blow mold, which is used to make the container is provided according to the invention comprises two Outer shapes and a central shape, with the individual parts of the glass tool in the usual way on mold platens are mounted, which can be moved within a closing frame are. The outer forms are away from each other and to each other in the sense of an opening and closing movement the glass tool can be moved. The center shape is transverse to the opening and closing movement of the outer molds movable. The center shape includes pneumatically adjustable or slidable component holder, with which internals in the produced Containers are placeable. The container according to the Invention is as a multilayer extruded fuel tank made of thermoplastic material.

The method comprises ejecting web-shaped preforms from extrusion heads, wherein the preforms are each cut to length between the outer molds and the center mold. The outer shapes are closed with respect to the center shape. The preforms are drawn or pressed by means of gas pressure and / or by means of externally applied vacuum in the part cavities formed by the outer molds of the tool. In a further step, for example, that on the component holder 2 placed connection element 3 towards an outer mold (blow mold 1 ), so that the connecting element 3 the wall 4 of the preform 5 pierces. Then, for example, the in 2 illustrated component holder 2 pulled into the middle form, not shown. The outer shapes are moved apart, the center shape is moved transversely to the opening and closing movement between the outer molds, so that the outer shapes can close again and the meanwhile each half shells forming preforms can assemble into a closed container.

As already mentioned, the connecting element 3 be designed as a connection nipple on both sides of a circumferential collar 6 one each with a Christmas tree profile 7 provided thong 8th formed. In terms of the wall 4 of the preform has the connection element 3 a leading end in the insertion direction 9 and a rear end in the insertion direction 10 , In the in the 1 to 3 shown variant of the connection element 3 is on the leading end 9 a hollow, sleeve-shaped cutting element 11 attached, the one front circumferential cutting edge 12 having. The cutting edge 12 is wave-shaped and has a crown-shaped profile, whereby the piercing of the wall 4 of the preform 5 is simplified. The cutting edge 12 does not necessarily have to be wave-shaped, but this may also be the contour of the in 4 Having shown cutting element. At the cutting edge 12 distant end of the cutting element 11 this is with inwardly projecting, resilient locking projections 13 provided in a circumferential detent recess 14 on the circumference of the pin 8th snap in the connection element. The locking projections 13 can each be provided on detent springs of the cutting element, which can be formed, for example, by correspondingly formed longitudinal slots thereof.

At the pin 8th of the connection element 3 at its leading end 9 is also an encircling stop 15 for the cutting element 11 intended.

The cutting element forms in the region of the circumferential cutting edge 12 a first, in the insertion direction leading melt chamber 16 out. Behind it in the insertion direction is a second melt chamber 17 intended. The melt chambers 16 . 17 are interconnected by a melt channel 18 connected.

In the wall of the blow molding tool 1 is a recess 19 provided, which forms a die, the diameter of the diameter of the cutting element in its diameter 11 equivalent. How this from the synopsis of 1 to 3 it can be seen that is on the component holder 2 plugged connection element 3 by means of the component holder 2 in the wall 4 of the preform 5 pushed in, while the case of the cutting element 11 penetrated and displaced plastic material into the recess 19 is pressed into it. Partially, the material flows into the first 16 and optionally through the melt channel 18 into the second melt chamber 17 ,

2 shows the retracted component holder and completely the wall 4 of the preform 5 penetrating connection element, wherein the circumferential collar 6 of the connection element 3 all over the wall 4 is present and with the still plastic wall of the preform 5 welded.

After completion of the article in the blow mold, the cutting element 11 like this in 3 is illustrated, from the outwardly projecting pin 8th of the connection element 3 be removed.

The connection element 3 in the embodiment described above is formed symmetrically as a nipple or double nipple, both sides of the circumferential collar 6 one pin each 8th with fir tree profile 7 are provided, both pins have approximately the same length and the profiling 8th the pin is identical, so that the cutting element 11 on each side of the connection element 3 can be plugged.

To form the melt chambers 16 . 17 is the cutting element 11 with an inner subdivision 20 provided by the melt channel 18 is interspersed. Instead of a melt channel 18 It is also possible to provide a plurality of melt channels.

At the in 4 illustrated variant of the connection element 3 this is at its leading end 9 with a cutting element 11 provided that not as a removable sleeve, but as an integral part of the connecting element 3 is trained. The leading end 9 of the connecting element is widened like a sleeve and with a circumferential cutting edge 12 provided in the in 4 shown sectional view is curved arcuate. This particular geometry of the cutting edge allows a penetration or punching of the wall of the container with relatively low penetration resistance to excessive Ausulpung the wall 4 to prevent the container. The cutting element can be separated as needed after completion of the container in a post-processing step.

To the weldability of the collar 6 or of the circumferential flange of the connection element 3 with the wall 4 to improve the container is at the in 4 shown variant of the connection element 3 on the wall 4 facing surface 21 of the collar 6 a profiling provided. Due to the sawtooth-like structure of the surface 21 the heat capacity of the plastic is partially reduced, so that an easy weldability with the wall 4 the container is guaranteed.

1

blow molding

2

component holder

3

connecting element

4

wall

5

preform

6

collar

7

Tannenbaum profile

8th

spigot

9

leader The End

10

rear The End

11

cutting element

12

cutting edge

13

latching projections

14

latching depression

15

attack

16

first melt chamber

17

second melt chamber

18

melt channel

19

recess

20

subdivision

21

area

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1211196 [0005]
• - EP 1211196 A1 [0005, 0005]

Claims (13)

Method for producing a container made of thermoplastic material by extrusion blow molding, wherein the container during its formation within a multi-part tool with at least one wall thereof passing through connecting element is provided, wherein the wall the container in a still plasticized state with a Part of the connecting element is pierced such that the connection element at least in partial areas with the container wall enters a substance-liquid connection, wherein the connecting element is provided with a penetrating tip and the connecting element in the penetration of the container wall into one in the tool provided die is inserted, which is on the connecting element the opposite side of the container wall is arranged or is arranged. Method according to claim 1, characterized in that that a nipple is used as a connecting element, which with a circumferential flange for welding to the container wall is provided. Method according to one of claims 1 or 2, characterized in that as a penetrating tip a sleeve-shaped Cutting element application that removes on the connecting element is put on. Connection element ( 3 ) for use in a method according to any one of claims 1-3, characterized in that it is designed as a tubular penetrating element with a circumferential collar ( 6 ) is designed for welding to the container wall and that a part of the connecting element with a circumferential cutting edge ( 12 ) is provided. Connecting element according to claim 4, characterized in that the peripheral cutting edge ( 12 ) in a longitudinal center plane of the connecting element ( 3 ) is curved. Connecting element according to claim 5, characterized in that the connecting element ( 3 ) is formed in two parts and that the cutting element ( 11 ) is sleeve-shaped and provided for piercing the wall insertion side of the connecting element ( 3 ) encloses. Connecting element according to claim 6, characterized in that the cutting element ( 11 ) with the connection element ( 3 ) is locked. Connecting element according to one of claims 6 or 7, characterized in that this as a nipple with at least one outer retaining profile ( 7 ), wherein the retaining profile ( 7 ) positively with the cutting element ( 11 ) cooperates. Connecting element according to one of claims 5-8, characterized in that the cutting element ( 11 ) as an approximately cylindrical sleeve with a leading in mounting position, circumferential cutting edge ( 12 ) is trained. Connecting element according to claim 9, characterized in that the cutting edge ( 12 ) is formed wavy. Connecting element according to one of the connections 6-10, characterized in that the cutting element ( 11 ) in the longitudinal direction at least one subdivision ( 20 ), through which at least one in the cutting direction front and rear melt chamber ( 16 ) 17 ) is formed. Connection element according to claim 11, characterized in that the melt chambers ( 16 ) 17 ) at least via a melt channel ( 18 ) communicate with each other. Connection element according to one of the claims 1 to 12, characterized in that the connecting element in one piece is formed on a functional component.